Alternating Current [AC]distribution systems operate most efficiently with a distortion free sine wave voltage present. When an AC distribution system has nonlinear loads, typically distortion voltage is introduced by such nonlinear loads into the AC distribution system. These distortions are illustratively represented in the sine wave shown in FIG. 1 for a given AC distribution system.
Attempts to correct the distortion voltage, also known as the harmonic part of the voltage, have included adding active power filters to the AC distribution system. See, for instance, U.S. Pat. No. 3,825,815 which provides for the ability to compensate for the distortion voltage. Heretofore, there have been no filters that could compensate for the distortion voltage completely, as well as provide voltage regulation in order to insure a voltage with the proper amplitude.
Moreover, these prior art active filters must be sized according to the high power distortion producing nonlinear loads. This requires that the filter must be capable of providing high peak compensating currents.
The present invention is capable of compensating for the distortion voltage as well as provide voltage regulation. Additionally, the present invention is capable of zone filtering. That is, the present invention is capable of providing the power required by the sensitive, usually low power loads in a zone and protecting them from the distortion voltage due to the nonlinear loads in another zone of the AC distribution system.